2i6k
From Proteopedia
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'''Crystal structure of human type I IPP isomerase complexed with a substrate analog''' | '''Crystal structure of human type I IPP isomerase complexed with a substrate analog''' | ||
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[[Category: Wei, Z.]] | [[Category: Wei, Z.]] | ||
[[Category: Zhang, C.]] | [[Category: Zhang, C.]] | ||
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Revision as of 04:08, 4 May 2008
Crystal structure of human type I IPP isomerase complexed with a substrate analog
Overview
Type I isopentenyl diphosphate (IPP): dimethylally diphosphate (DMAPP) isomerase is an essential enzyme in human isoprenoid biosynthetic pathway. It catalyzes isomerization of the carbon-carbon double bonds in IPP and DMAPP, which are the basic building blocks for the subsequent biosynthesis. We have determined two crystal structures of human IPP isomerase I (hIPPI) under different crystallization conditions. High similarity between structures of human and Escherichia coli IPP isomerases proves the conserved catalytic mechanism. Unexpectedly, one of the hIPPI structures contains a natural substrate analog ethanol amine pyrophosphate (EAPP). Based on this structure, a water molecule is proposed to be the direct proton donor for IPP and different conformations of IPP and DMAPP bound in the enzyme are also proposed. In addition, structures of human IPPI show a flexible N-terminal alpha-helix covering the active pocket and blocking the entrance, which is absent in E. coli IPPI. Besides, the active site conformation is not the same in the two hIPPI structures. Such difference leads to a hypothesis that substrate binding induces conformational change in the active site. The inhibition mechanism of high Mn(2+) concentrations is also discussed.
About this Structure
2I6K is a Single protein structure of sequence from Homo sapiens. Full crystallographic information is available from OCA.
Reference
Crystal structures of human IPP isomerase: new insights into the catalytic mechanism., Zhang C, Liu L, Xu H, Wei Z, Wang Y, Lin Y, Gong W, J Mol Biol. 2007 Mar 9;366(5):1437-46. Epub 2006 Nov 3. PMID:17137593 Page seeded by OCA on Sun May 4 07:08:26 2008
